The disclosure relates generally to adjustment and control of a jack, and more particularly to adjustment and control of stop gaps in a hydraulic jack.
In the assembly and/or disassembly of double-wall gas turbine casing assemblies, roller jacks may be employed to move portions of the assemblies. For example, a lower half of a casing assembly may be supported on roller jacks after removal of the upper half for access to the interior of the gas turbine. Because typical double-wall casing assemblies are very heavy, the roller jacks that are employed are usually hydraulic jacks, which can handle very large loads despite being relatively small and easy to handle. However, fine tuning the positioning of a hydraulic jack can be difficult, which may lead to improper alignment and/or damage of tight assembly clearance parts of gas turbines with which they are used. For example, overshoot during extension of a hydraulic jack may cause a collision of the casing into a turbine blade tip. In addition, hydraulic jacks have a tendency to retract under load if left extended for a period of time so that repositioning may become necessary if a user leaves the jack to adjust another portion of the casing assembly.